Obesity is an 'epidemic' within the UK. Individuals living with obseity are at risk of developing cancer, heart problems and dieing. Furthermore, obesity impacts on psychological wellbeing via lowered self-efficacy, self-esteem, body image and overall quality of life (QoL). A pilot randomised controlled trial (RCT) is proposed to investigate the additional benefit of a psychological intervention alongside treatment as usual (TAU) in a weight management service. Patients routinely attending an outpatient clinic will be randomised into TAU with or without additional acceptance and commitment Therapy (ACT) group based-input and their outcomes monitored over time.